Running and shipping elevate plasma levels of beta-endorphin-like substance (B-END-LI) in thoroughbred horses

Comparative endocrinological responses to short transportation of Equidae (Equus asinus and Equus caballus)

In order to evaluate the effects of short transportation on β-endorphin, adrenocorticotropic hormone (ACTH) and cortisol changes, 12 healthy stallions of Equidae (Equus asinus and Equus caballus) were studied before and after transportation of 50 km. Blood samples were collected 1 week before transportation in basal conditions, immediately before loading and after transportation and unloading, on their arrival at the breeding station. Compared to basal and before values, donkeys showed an increase in circulating ACTH (P < 0.001) and cortisol (P < 0.0005) levels after transportation and higher ACTH (P < 0.01) levels than horses after transportation. A positive and significant correlation (r = 0.885; P < 0.01) between ACTH and cortisol levels after transportation was found. No significant differences were observed for β-endorphin levels. Compared to basal and before values, horses showed higher cortisol (P < 0.005) levels after transportation and no significant differences were observed for ACTH and β-endorphin levels in donkeys. Horses facing forward (direction of travel) showed higher (P < 0.01) β-endorphin levels after transportation than donkeys; horses facing backward (the opposite direction of travel) showed lower (P < 0.05) ACTH levels after transportation. The results indicate that short transportation induces a preferential activation of the hypothalamus-pituitary-axis (HPA), with significant release of ACTH and cortisol in donkeys and only of cortisol in horses, suggesting that transportation for donkeys may be more stressful than horses.

Circulating beta-endorphin, adrenocorticotrophic hormone and cortisol levels of stallions before and after short road transport: stress effect of different distances

Background

Since transport evokes physiological adjustments that include endocrine responses, the objective of this study was to examine the responses of circulating β-endorphin, adrenocorticotrophic hormone (ACTH) and cortisol levels to transport stress in stallions.

Methods

Forty-two healthy Thoroughbred and crossbred stallions were studied before and after road transport over distances of 100, 200 and 300 km. Blood samples were collected from the jugular vein: first in a single box immediately before loading (pre-samples), then immediately after transport and unloading on arrival at the breeding stations (post-samples).

Results

An increase in circulating β-endorphin levels after transport of 100 km (P < 0.01), compared to basal values was observed. Circulating ACTH levels showed significant increases after transport of 100 km (P < 0.001) and 200 km (P < 0.001). Circulating cortisol levels showed significant increases after road transport over distances of 100, 200 and 300 km (P < 0.001). An effect of transport on β-endorphin, ACTH and cortisol variations was therefore evident for the different distances studied. No significant differences (P > 0.05) between horses of different ages and different breeds were observed for β-endorphin, ACTH and cortisol levels.

Conclusion

The results obtained for short term transportation of stallions showed a very strong reaction of the adrenocortical system. The lack of response of β-endorphin after transport of 200–300 km and of ACTH after transport of 300 km seems to suggest a soothing effect of negative feedback of ACTH and cortisol levels.

The endocrine system and the challenge of exercise

Fine-tuning of the response to exercise that lasts longer than a few seconds is reliant on the regulation of several key variables governing the cardiopulmonary, vascular, and metabolic response to exercise. This type of integrative response requires communication between organ systems that relies on the secretion of endocrine and paracrine substances by one tissue or organ that are transported remotely to other tissues or organs to evoke a response to adjust to the disturbance.

Effect of the microclimate on horses during international air transportation in an enclosed container

OBJECTIVE

To determine if the microclimate is detrimental to horses during international air transportation in an enclosed container.

PROCEDURE

On each of two 12 h and two 24 h flights three horses were transported in an enclosed container designed to prevent exposure to insect vectors. Heart rates were monitored throughout and blood samples were collected periodically. Air in the container was sampled for bacteria and fungal spores and the temperature and relative humidity were recorded inside and outside the container periodically during the flight. On the two 12 h flights similar observations were made on three horses transported in regular open containers, which were used as controls.

RESULTS

Heart rates during the flights reflected any agitation of the horses. Agitation was only mild and generally associated with take-off and landing. There were no changes in haematological or blood biochemical values that suggested any detrimental effects of the flights. The temperature in the Airstable was relatively constant during each flight (means ranged from 18.7 to 23.4 degrees C) and was significantly warmer than in the cargo hold (range 13.9 to 18.3 degrees C). Relative humidity fluctuated more widely and reflected the ambient humidity during airport stops. The numbers of bacteria and fungal spores in the Airstable air varied during the flights but were of no apparent significance to the horses' health.

CONCLUSION

The Airstable proved a convenient means to transport horses on international flights and caused no discernible ill effects on the horses studied.

Metabolic, hormonal, and hemodynamic changes during dopamine infusions in halothane anesthetized horses

Selected metabolites, hormones and cardiovascular variables were measured in halothane anesthetized horses during 1 hour of dopamine infusion at a rate of 5 micrograms/kg/min (low) and 10 micrograms/kg/min (high), and for 1 hour after infusion. Plasma cortisol increased twofold in the low-infusion group but did not change significantly in the high-infusion group. Plasma nonesterified fatty acids, blood glucose, blood lactate, and plasma insulin increased in the high-infusion group. There was little difference in heart rate, systolic, diastolic, and mean arterial blood pressure between the two groups. The high infusion was associated with arrhythmias in several horses, and one horse showed ventricular fibrillation and died. If metabolic and hormonal changes are used as markers of a "stress response" in anesthetized horses the results must be carefully interpreted if a sympathomimetic agent such as dopamine is administered to maintain cardiovascular stability.

Narcotics and local anesthetics

The recognition and alleviation of animal pain is a growing veterinary and public concern. Pain can be of an acute or chronic nature with different behavioral manifestations. Physiologically, pain is a dynamic and complex phenomenon that produces changes in the central and autonomic nervous systems as well as in the endocrine system. Horses and other animals appear to possess an endogenous pain-suppressing system involving the brainstem and spinal cord. This system can modulate pain perception and the responses to it. The recently discovered endogenous opioid peptides (endorphins and enkephalins) appear to play a role in this system, which is activated by stress. Opioids (narcotic analgesics) act to selectively depress pain-sensitive cells. Opioid analgesics may act via multiple opioid receptors. Each subclass of opioid receptor has a different pharmacologic profile. Classical opioids that act at mu (morphine) receptors typically produce analgesia, increased locomotor activity, cardiorespiratory stimulation, and a decrease in intestinal peristalsis in the horse. Opioids that act at kappa receptors produce analgesia, sedation, ataxia, and minimal autonomic effects in the horse. Owing to their lack of excitatory actions, the kappa opioids represent a potentially useful class of analgesics for use in equine species. Local anesthetics depress all excitable cells and can diminish sensory, motor, and muscular function. They do not act selectively on pain fibers, although pain is among the first sensations lost following a nerve block. Local anesthetic activity is enhanced by increased extraneuronal pH, nerve cooling, increased nervous activity, coadministration of a vasoconstrictor or hyaluronidase, delayed systemic absorption, prolonged drug metabolism, and by using agents with high lipid solubility. Procaine, lidocaine, and mepivacaine are among the most widely used and studied agents in horses. These agents and/or their metabolites can be readily detected in urine; in some cases, for prolonged periods.

Porcine endometrial epithelial cells immortalized by transfection with origin-defective, temperature-sensitive simian virus 40 DNA

The purpose of this study was to immortalize porcine endometrial cells and to characterize the transformed cells. Primary porcine endometrial cells were transfected with the plasmid vector (pmk16) containing SV40 DNA using a liposome-mediated method. The viral DNA was from a replication-defective, origin-minus, temperature-sensitive mutant strain (A58). One clone, designated PE-1, has been propagated for over 120 passages. PE-1 cells grown at 33C (33C cells) exhibit spindle-shaped morphology; when cultured at 40C (40C cells), they took on a polygonal or spherical shape. Morphology of 40C cells returned to the spindle shape after culture flasks were shifted back to 33C. During a 2-week period, 33C cells propagated approximately 30-fold faster than 40C cells, whereas protein concentration was higher in 40C cells. Southern blot analysis of PE-1 cells demonstrated successful integration of the ts-SV40 DNA sequence into the porcine endometrial cells, possibly at multiple sites. The presence of cytokeratin on PE-1 cell membranes was shown by immunocytochemical studies, suggesting that the PE-1 cell clone was of epithelial origin. Reverse phase (RP)-HPLC analysis of PE-1 cell extract indicated that the majority of immunoreactive beta-endorphin (ir-BEND) eluted with a hydrophobicity similar to that of synthetic BEND and alpha-N-acetylated BEND (Nac-BEND). These results demonstrate that a porcine endometrial cell line has been established, and that this cell line possesses characteristics of temperature sensitivity in cell morphology, growth rate, and protein synthesis.

Metabolic and hormonal changes associated with arthroscopic surgery in the horse

The effect of general anaesthesia and arthroscopic surgery on blood glucose and lactate, plasma non-esterified fatty acids, insulin, beta-endorphin and cortisol was investigated in seven horses. Animals were premedicated with xylazine and anaesthesia was induced with guaifenesin and sodium thiamylal and maintained with halothane vaporised in oxygen. Blood samples were collected in the pre-, intra- and post operative period. Induction of anaesthesia was associated with a transient hyperglycaemia and a significant rise in plasma insulin levels. Plasma insulin values fell during surgery but showed a significant increase post operatively. Surgery stimulated a small but significant rise in plasma beta-endorphin and cortisol values but these had returned to baseline values in the early post operative period. No changes in blood lactate were recorded.